A 6-series aluminum alloy sheet having a low zinc content and a method of manufacturing the same

Abstract

This invention relates to the field of aluminum alloy materials technology, specifically to a low-zinc-content 6-series aluminum alloy sheet and its manufacturing method. The components and their weight percentages in the low-zinc-content 6-series aluminum alloy sheet are as follows: Si content 0.90-1.20%, Mg content 0.45-0.65%, Cu content 0.12-0.20%, Zn content 0.05-0.10%, Fe content ≤0.28%, Mn content 0.02-0.20%, Cr content ≤0.10%, Ti content ≤0.15%, containing at least one of In, Cd, La, and Ce, and the total content of In, Cd, La, and Ce is 0.01-0.10%; the content of a single impurity ≤0.03%; the total content of other impurity elements ≤0.1%; and the balance is Al. This 6-series aluminum alloy sheet, with a low zinc content (Zn ≤0.10%), possesses excellent formability, high bake hardening value, and high batch stability.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to a low-zinc-content 6-series aluminum alloy sheet and its manufacturing method. Background Technology

[0002] The technical field of 6016 aluminum alloy is automotive lightweight materials, particularly aluminum alloy sheet technology for exterior body panels. Currently, the development of this field is primarily driven by the automotive industry's core demands for lightweighting, safety, and economy. Automakers require body panels to possess two seemingly contradictory properties: firstly, before stamping (T4P state), the material needs low yield strength and high elongation to ensure stamping accuracy and yield for complex shapes; secondly, after the paint line's baking process, the material needs to achieve a significant strength increase (i.e., high bake-hardening (BH) effect) to enhance the dent resistance of the body panels.

[0003] To meet the aforementioned development needs, especially to enhance the bake hardening (BH) effect of 6016 aluminum alloy, existing technologies mainly employ two mainstream improvement routes: 1. High-zinc (Zn) alloying: By adding a higher content of Zn (e.g., ≥0.3-0.5 wt.%) to the Al-Mg-Si alloy, the BH value can be significantly improved. While adding a high Zn content can increase the BH value, it also brings negative effects such as reduced corrosion resistance and increased alloy costs. More importantly, it causes the initial yield strength in the T4P state before stamping to rise prematurely, which directly impairs its stamping performance and narrows the process window; 2. Isothermal pre-aging... The PA process, which uses heat treatment to regulate properties, involves immediately subjecting aluminum alloy sheets to a short isothermal heat treatment after solution quenching, such as holding at 160°C for 15 minutes, to stabilize the microstructure and regulate subsequent aging behavior. However, the isothermal PA process has limited ability to regulate the microstructure and struggles to achieve the best balance between effectively suppressing natural aging (NA) and maximizing the retention of BH precipitation potential. Furthermore, due to its sensitivity to minor fluctuations in the production process, the performance of materials using this process varies significantly between batches.

[0004] Existing technologies generally lack process feedback control, limiting only static parameters such as chemical composition or process temperature / time, and lacking online monitoring and dynamic feedback adjustment mechanisms for the intermediate state of materials during production. This is one of the fundamental reasons for poor batch-to-batch consistency of product performance.

[0005] In summary, there is an urgent need to solve the technical problem that existing technologies struggle to achieve excellent formability, high bake hardening value, and high batch stability in 6-series aluminum alloys with low zinc content (Zn≤0.10%). Summary of the Invention

[0006] The present invention aims to solve the technical problem of how to provide a 6-series aluminum alloy that has excellent formability, high bake hardening value and high batch stability under low zinc content (Zn≤0.10%).

[0007] To achieve the above objectives, the first aspect of the present invention provides a low-zinc-content 6-series aluminum alloy sheet, wherein the components and their weight percentages in the low-zinc-content 6-series aluminum alloy sheet are as follows:

[0008] The Si content is 0.90-1.20%.

[0009] The Mg content is 0.45-0.65%;

[0010] The Cu content is 0.12-0.20%;

[0011] The Zn content is 0.05-0.10%;

[0012] Fe content ≤ 0.28%;

[0013] The Mn content is 0.02-0.20%;

[0014] Cr content ≤ 0.10%;

[0015] Ti content ≤ 0.15%;

[0016] It contains at least one of In, Cd, La, and Ce, and the total content of In, Cd, La, and Ce is 0.01-0.10%;

[0017] The content of a single impurity is ≤0.03%;

[0018] The total content of other impurity elements is ≤0.1%;

[0019] The balance is Al.

[0020] The second aspect of the present invention provides a method for manufacturing the above-mentioned low-zinc-content 6-series aluminum alloy sheet, wherein the manufacturing method includes melting, casting, homogenization, hot rolling, cold rolling, annealing and solution treatment, pre-aging, and intermediate state feedback.

[0021] The pre-aging process includes three sections: the first section has a temperature of 95-110℃ and a time of 2-5 minutes, cooling down to 70-85℃ at a first cooling rate of 1-3℃ / s; the second section has a temperature of 70-85℃ and a time of 2-5 minutes, cooling down to 45-60℃ at a second cooling rate of 0.5-2℃ / s; and the third section has a temperature of 45-60℃ and a time of 3-6 minutes.

[0022] The total pre-aging time is 7-16 minutes.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) By using the alloy system of “low Zn + appropriate amount of Cu”, the common problems of corrosion resistance reduction and excessive yield strength of high Zn system are avoided. At the same time, the bake hardening (BH) response is significantly enhanced. The introduction of In / Cd / La / Ce trace elements effectively suppresses natural aging (NA), ensuring that the material maintains a low yield strength and good formability before stamping. The strength is greatly improved after baking, which meets the dual requirements of “forming + baking” for automotive outer panels.

[0025] (2) By controlling the hot rolling final rolling temperature and coiling temperature, "hot rolling self-annealing" is realized, replacing the traditional intermediate annealing process, which significantly simplifies the production process, saves energy and time in the intermediate annealing process, reduces the overall manufacturing cost, and improves production efficiency.

[0026] (3) Hot rolling self-annealing promotes recrystallization and texture homogenization of the sheet, reducing anisotropic defects in the strip during subsequent stamping. Pre-aging adopts a non-isothermal multi-stage cooling process, which realizes efficient nucleation and controlled growth of the strengthening phase, avoids the inhomogeneity caused by excessive growth of the cluster phase, and significantly improves batch stability.

[0027] (4) This invention is the first to use “conductivity + TTA” as an intermediate performance control index. Combined with online monitoring and automatic parameter adjustment, a closed-loop feedback system is established. This measure effectively avoids performance fluctuations caused by natural aging or differences in transportation and storage, thereby significantly improving the batch consistency and reliability of the product.

[0028] (5) The sheet material provided by this invention has low yield strength, excellent elongation and formability in the T4P state, which facilitates the stamping and forming of automotive outer panels. After baking (185℃×20min), both yield strength and tensile strength are significantly improved, which can meet the requirements of automotive outer panels for strength and dent resistance. It is superior to existing similar technologies in terms of corrosion resistance, cost control and batch consistency, and has significant industrial application value. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] In existing technologies, it is difficult for 6-series aluminum alloys to achieve a low yield strength (Rp) before stamping.0.2 =95-120MPa) and high elongation (A 50 ≥24%) to ensure formability, while also possessing extremely high strength (ΔRp) after coating and baking. 0.2 ≥115-130MPa) to ensure dent resistance.

[0031] In this invention, the inventors discovered that by using a specific alloy ratio, along with other optimization methods and specific hot-rolled annealing, non-isothermal multi-stage pre-aging, and feedback mechanisms for electrical conductivity and transport time, it is possible to produce 6-series aluminum alloys with excellent formability, high bake hardening value, and high batch stability under low zinc content (Zn≤0.10%). This solves the problem of excessively rapid increase in yield strength caused by natural aging (NA) during storage and transport of sheet metal in the T4P state, controlling the yield strength increment within 7 days to within 15MPa, thereby ensuring stable stamping performance. It also solves the problem of large batch-to-batch fluctuations in final product performance caused by the lack of online process monitoring and feedback adjustment, reducing performance fluctuations by more than 30%.

[0032] Therefore, in a first aspect, the present invention provides a low-zinc-content 6-series aluminum alloy sheet, wherein the components and their weight percentages in the low-zinc-content 6-series aluminum alloy sheet are as follows:

[0033] The Si content is 0.90-1.20%.

[0034] The Mg content is 0.45-0.65%;

[0035] The Cu content is 0.12-0.20%;

[0036] The Zn content is 0.05-0.10%;

[0037] Fe content ≤ 0.28%;

[0038] The Mn content is 0.02-0.20%;

[0039] Cr content ≤ 0.10%;

[0040] Ti content ≤ 0.15%;

[0041] It contains at least one of In, Cd, La, and Ce, and the total content of In, Cd, La, and Ce is 0.01-0.10%;

[0042] The content of a single impurity is ≤0.03%;

[0043] The total content of other impurity elements is ≤0.1%;

[0044] The balance is Al.

[0045] In this invention, the low-zinc-content 6-series aluminum alloy sheet is a low-Zn-Cu main strengthening system. Zn is limited to 0.05-0.10% to avoid the risks of decreased corrosion resistance, increased cost, and excessively high T4P yield strength caused by high Zn content. Cu is limited to 0.12-0.20% as the main contributing element to bake hardening performance. High-binding-energy In / Cd / La / Ce elements are introduced to capture supersaturated vacancies after quenching, forming a solute-vacancy complex. This complex can suppress natural aging (NA) and release vacancies during baking, accelerating β-hardening. ” Phase precipitation enhances the BH response.

[0046] According to the present invention, under the condition of storage at 20-30℃ in the T4P state for 7-12 days, the yield strength Rp of the low zinc content 6-series aluminum alloy sheet is... 0.2 The strength is 95-120 MPa, and the elongation is A. 50 It is 24-30%;

[0047] T4P state refers to the state of the sheet metal before stamping, after solution treatment and quenching, and natural aging at 20-30℃ for 7-12 days.

[0048] In this invention, the quenching includes a pre-aging treatment.

[0049] Baking hardening increment ΔRp 0.2 It is 115-130 MPa.

[0050] The second aspect of the present invention provides a method for manufacturing the above-mentioned low-zinc-content 6-series aluminum alloy sheet, wherein the manufacturing method includes melting, casting, homogenization, hot rolling, cold rolling, annealing and solution treatment, pre-aging, and intermediate state feedback.

[0051] The pre-aging process includes three sections: the first section has a temperature of 95-110℃ and a time of 2-5 minutes, cooling down to 70-85℃ at a first cooling rate of 1-3℃ / s; the second section has a temperature of 70-85℃ and a time of 2-5 minutes, cooling down to 45-60℃ at a second cooling rate of 0.5-2℃ / s; and the third section has a temperature of 45-60℃ and a time of 3-6 minutes.

[0052] The total pre-aging time is 7-16 minutes.

[0053] In this invention, a specific non-isothermal multi-short pre-aging (PA) process can achieve "high-temperature nucleation and low-temperature growth suppression," inhibiting nucleation (NA) and preserving the potential of biogenic hematopoiesis (BH).

[0054] According to the present invention, the homogenization conditions include: a homogenization temperature of 530-560°C and a homogenization time of 6-16 hours.

[0055] In this invention, specific homogenization can eliminate segregation and coarse intermetallic compounds.

[0056] According to the present invention, the hot rolling conditions include: a final rolling temperature of 510-530°C, a coiling temperature of 340-380°C, a holding temperature of 1-2 hours, and self-annealing to 220-260°C through coiling preheating.

[0057] In this invention, the roughing of hot rolling adopts conventional process parameters in the field, as long as they meet the requirements of subsequent processing.

[0058] The hot rolling annealing of this invention eliminates the traditional annealing process, simplifying the process and reducing energy consumption.

[0059] According to the present invention, the conditions for cold rolling include: a cold rolling reduction rate of ≥50% and a sheet thickness of 0.8-2.0 mm.

[0060] According to the present invention, the annealing and solution treatment conditions include: heating at a temperature of 540-550°C, holding at that temperature for 20-60 seconds, and then spraying or quenching at a third cooling rate of ≥80°C / min to 30-60°C.

[0061] In this invention, specific annealing and solution treatment conditions ensure that the elements are fully dissolved.

[0062] According to the present invention, the conditions for the intermediate state feedback include: the conductivity of the plate is tested to be 28-31 MS / m 1-2 hours after the pre-aging is completed; if the conductivity is >31 MS / m, the heating temperature in the annealing solution is increased by 5-15°C; if the conductivity is <28 MS / m, the heating temperature in the annealing solution is decreased by 5-15°C.

[0063] Alternatively, after the pre-aging is completed, the conductivity of the plate is tested 1-2 hours later and it meets the requirement of 28-31 MS / m. If the conductivity is >31 MS / m, the plate running speed of the solution furnace is reduced by 5-20%. If the conductivity is <28 MS / m, the plate running speed of the solution furnace is increased by 5-20%.

[0064] According to the present invention, the time from pre-aging to stamping is ≤96h. If the time from pre-aging to stamping is >96h, a stabilization treatment is performed before stamping, specifically, the sample is placed at 90-100℃ for 5-8min.

[0065] In this invention, the smelting and casting adopt conventional process parameters in the field, as long as they meet the requirements of subsequent processing.

[0066] According to some embodiments of the present invention, the smelting conditions include: a smelting temperature of 730-760°C and a smelting time of 2-4 hours;

[0067] The casting conditions include a casting rate of 3-6 m / h.

[0068] Test methods

[0069] Yield strength Rp 0.2 Measured according to ISO 6892-1 (Metallic materials, tensile test at room temperature).

[0070] Elongation A 50 Measured according to ISO 6892-1 (Metallic materials, tensile test at room temperature).

[0071] Baking hardening properties include baking hardening increment ΔRp 0.2 The test method is as follows: first, the yield strength in the T4P state is tested according to ISO 6892-1 (Metallic materials, tensile testing at room temperature): 2% pre-stretching followed by baking at 185℃ for 20 min; then, the yield strength is tested according to ISO 6892-1 (Metallic materials, tensile testing at room temperature). The difference between the two is ΔRp. 0.2 .

[0072] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. All other embodiments implemented by those skilled in the art based on the embodiments of the present invention without creative improvements are within the protection scope of the present invention.

[0073] The components and their weight percentages in 6-series aluminum alloy sheets are as follows: Si 1.0%, Mg 0.55%, Cu 0.18%, Zn 0.08%, La 0.02%, Fe 0.15%, Mn 0.05%, Cr 0.03%, Ti 0.02%, with the balance being Al. The content of a single impurity is ≤0.03%, and the total content of other impurity elements is ≤0.1%.

[0074] Melting: Melting temperature 745℃, melting time 3 hours;

[0075] Casting: Ingot casting rate 4.5 m / h;

[0076] Homogenization: 545℃×10h;

[0077] Hot rolling: The final rolling temperature is 515℃, the coiling temperature is 360℃, the holding temperature is 1.5h, and the temperature is annealed to 240℃.

[0078] Cold rolling: The cold rolling reduction rate is 65%, and the thickness of the sheet obtained by cold rolling is 1.2 mm;

[0079] Annealing and solution treatment: After holding at 545℃ for 30s, spray quenching is performed with a spray cooling rate of 100℃ / min to 40℃.

[0080] Pre-aging: The temperature of the first section is 105℃, the time of the first section is 3 minutes, and the temperature is reduced to 80℃ at a first cooling rate of 2℃ / s; the temperature of the second section is 80℃, the time of the second section is 3 minutes, and the temperature is reduced to 55℃ at a second cooling rate of 1℃ / s; the temperature of the third section is 55℃, and the time of the third section is 4 minutes; the total pre-aging time is 10 minutes.

[0081] Intermediate feedback: The electrical conductivity of the plate is tested 1 hour after pre-aging to be 28-31 MS / m. The time from pre-aging to stamping is ≤96 hours, and 6-series aluminum alloy plate A1 is obtained.

[0082] Example 2

[0083] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the components and their weight percentages in the 6-series aluminum alloy sheet were: Si 0.9%, Mg 0.45%, Cu 0.12%, Zn 0.05%, In 0.01%, Fe 0.10%, Mn 0.02%, Cr 0.01%, and Ti 0.01%, thus obtaining 6-series aluminum alloy sheet A2.

[0084] Example 3

[0085] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the components and their weight percentages in the 6-series aluminum alloy sheet were: Si 1.2%, Mg 0.65%, Cu 0.2%, Zn 0.1%, Cd 0.1%, Fe 0.28%, Mn 0.2%, Cr 0.1%, Ti 0.1%, and the resulting 6-series aluminum alloy sheet A3 was obtained.

[0086] Example 4

[0087] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the temperature of the first section was 95°C, the time of the first section was 2 min, and the temperature was reduced to 70°C at a first cooling rate of 1°C / s; the temperature of the second section was 70°C, the time of the second section was 2 min, and the temperature was reduced to 45°C at a second cooling rate of 0.5°C / s; the temperature of the third section was 45°C, and the time of the third section was 3 min; the total pre-aging time was 7 min, and the 6-series aluminum alloy sheet A4 was obtained.

[0088] Example 5

[0089] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the temperature of the first section was 110°C, the time of the first section was 5 min, and the temperature was reduced to 85°C at a first cooling rate of 3°C / s; the temperature of the second section was 85°C, the time of the second section was 5 min, and the temperature was reduced to 60°C at a second cooling rate of 2°C / s; the temperature of the third section was 60°C, and the time of the third section was 6 min; the total pre-aging time was 16 min, and the 6-series aluminum alloy sheet A5 was obtained.

[0090] Example 6

[0091] A6 series aluminum alloy sheet was prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 1 hour of pre-aging. The conductivity was >31 MS / m. The heating temperature in the annealing solution was increased by 10°C to obtain A6 series aluminum alloy sheet.

[0092] Example 7

[0093] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 2 hours of pre-aging. The conductivity was <28 MS / m. The heating temperature in the annealing solution was adjusted to decrease by 10°C to obtain the A7 6-series aluminum alloy sheet.

[0094] Example 8

[0095] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 1 hour of pre-aging. The conductivity was >31 MS / m. The sheet running speed during annealing and solution treatment was reduced by 10%, and the A8 6-series aluminum alloy sheet was obtained.

[0096] Example 9

[0097] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 2 hours of pre-aging. The conductivity was <28 MS / m. The sheet running speed during annealing and solution treatment was increased by 10%, and 6-series aluminum alloy sheet A9 was obtained.

[0098] Example 10

[0099] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1, except that the pre-aging to stamping time was >96 hours.

[0100] Before stamping, a stabilization treatment is performed by placing the sample at 90°C for 5 minutes to obtain A10 6-series aluminum alloy sheet.

[0101] Example 11

[0102] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1, except that the pre-aging to stamping time was >96 hours.

[0103] Before stamping, a stabilization treatment was performed by placing the sample at 100°C for 8 minutes to obtain 6-series aluminum alloy sheet A11.

[0104] Comparative Example 1

[0105] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the components and their weight percentages in the 6-series aluminum alloy sheet were: Si 1.0%, Mg 0.55%, Cu 0.08%, Zn 0.03%, La 0.02%, Fe 0.15%, Mn 0.05%, Cr 0.03%, Ti 0.02%, and a 6-series aluminum alloy sheet DA1 was obtained.

[0106] Comparative Example 2

[0107] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the components and their weight percentages in the 6-series aluminum alloy sheet were: Si 1.0%, Mg 0.55%, Cu 0.18%, Zn 0.30%, La 0.02%, Fe 0.15%, Mn 0.05%, Cr 0.03%, Ti 0.02%, and a 6-series aluminum alloy sheet DA2 was obtained.

[0108] Comparative Example 3

[0109] The 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the hot rolling process coiling temperature was 280°C, no self-annealing occurred, and a medium annealing process was adopted, with specific parameters of 380°C×2h, to obtain the 6-series aluminum alloy sheet DA3.

[0110] Comparative Example 4

[0111] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1, except that the pre-aging was carried out at a constant temperature of 100°C for 4 hours to obtain 6-series aluminum alloy sheet DA4.

[0112] Comparative Example 5

[0113] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the temperature of the first section was 85°C, the time of the first section was 2 min, and the temperature was reduced to 60°C at a first cooling rate of 1°C / s; the temperature of the second section was 60°C, the time of the second section was 2 min, and the temperature was reduced to 35°C at a second cooling rate of 0.5°C / s; the temperature of the third section was 35°C, and the time of the third section was 3 min; the total pre-aging time was 7 min, and a 6-series aluminum alloy sheet DA5 was obtained.

[0114] Comparative Example 6

[0115] A 6-series aluminum alloy sheet was prepared according to the manufacturing method of Example 1, except that the temperature of the first section was 120°C, the time of the first section was 5 min, and the temperature was reduced to 95°C at a first cooling rate of 3°C / s; the temperature of the second section was 95°C, the time of the second section was 5 min, and the temperature was reduced to 70°C at a second cooling rate of 2°C / s; the temperature of the third section was 70°C, and the time of the third section was 6 min; the total pre-aging time was 16 min, and the 6-series aluminum alloy sheet DA6 was obtained.

[0116] Comparative Example 7

[0117] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 1 hour of pre-aging. The conductivity was >31 MS / m. The heating temperature in the annealing solution was increased by 25°C to obtain 6-series aluminum alloy sheet DA7.

[0118] Comparative Example 8

[0119] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 2 hours of pre-aging. The conductivity was <28 MS / m. The heating temperature in the annealing solution was reduced by 25°C to obtain 6-series aluminum alloy sheet DA8.

[0120] Comparative Example 9

[0121] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 1 hour of pre-aging. The conductivity was >31 MS / m. The sheet running speed during annealing and solution treatment was reduced by 25% to obtain 6-series aluminum alloy sheet DA9.

[0122] Comparative Example 10

[0123] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1. The difference was that the intermediate state feedback was that the conductivity of the sheet was not 28-31 MS / m after 2 hours of pre-aging. The conductivity was <28 MS / m. The sheet running speed during annealing and solution treatment was increased by 25% to obtain 6-series aluminum alloy sheet DA10.

[0124] Comparative Example 11

[0125] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1, except that the pre-aging to stamping time was >96 hours.

[0126] Before stamping, a stabilization treatment was performed by placing the sample at 80°C for 3 minutes to obtain DA11 6-series aluminum alloy sheet.

[0127] Comparative Example 12

[0128] 6-series aluminum alloy sheets were prepared according to the manufacturing method of Example 1, except that the pre-aging to stamping time was >96 hours.

[0129] Before stamping, a stabilization treatment was performed, and the sample was placed at 110°C for 12 minutes to obtain DA12 6-series aluminum alloy sheet.

[0130] Table 1

[0131]

[0132] Yield strength Rp in Table 1 0.2 and elongation A 50 The T4P state was measured on 6-series aluminum alloy sheets stored at 23°C for 7 days.

[0133] By comparing the examples and comparative examples, it can be seen that the 6-series aluminum alloy sheets prepared in Examples 1-10 can significantly improve the strength increment after coating and baking while ensuring stable low yield and high elongation performance before stamping (T4P state). Furthermore, the consistency control of performance between batches can be achieved through online monitoring and dynamic parameter adjustment.

[0134] In Comparative Example 1, the 6-series aluminum alloy sheet had a severely insufficient Cu content, which prevented the formation of enough precipitation strengthening nuclei, resulting in a significant reduction in bake hardening response and ultimately failing to meet strength standards. In Comparative Example 2, the excessively high Zn content in the 6-series aluminum alloy sheet led to a significant increase in the initial yield strength in the T4P state and a decrease in elongation, severely damaging the material's stamping performance. Even though the BH value was acceptable, it lost its application value. In Comparative Example 3, the lack of a self-annealing step not only increased the additional energy consumption and processes of intermediate annealing but also led to an increase in the T4P state yield due to poor control of texture and recrystallization state, affecting the formability. In Comparative Example 4, the 6-series aluminum alloy sheet had insufficient inhibition of natural aging and insufficient retention of BH potential by single-stage isothermal PA, resulting in a high T4P state yield and a significantly reduced bake hardening value.

[0135] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-zinc-content 6-series aluminum alloy sheet, characterized in that, The components and their weight percentages in the low-zinc-content 6-series aluminum alloy sheet are as follows: The Si content is 0.90-1.20%. The Mg content is 0.45-0.65%; The Cu content is 0.12-0.20%; The Zn content is 0.05-0.10%; Fe content ≤ 0.28%; The Mn content is 0.02-0.20%; Cr content ≤ 0.10%; Ti content ≤ 0.15%; It contains at least one of In, Cd, La, and Ce, and the total content of In, Cd, La, and Ce is 0.01-0.10%; The content of a single impurity is ≤0.03%; The total content of other impurity elements is ≤0.1%; The balance is Al.

2. The low-zinc-content 6-series aluminum alloy sheet according to claim 1, characterized in that, The yield strength Rp of the low-zinc content 6-series aluminum alloy sheet was measured under the condition of storage at 20-30℃ in the T4P state for 7-12 days. 0.2 The strength is 95-120 MPa, and the elongation is A. 50 It is 24-30%; T4P state refers to the state of the sheet metal before stamping, after solution treatment and quenching, and natural aging at 20-30℃ for 7-12 days. Baking hardening increment ΔRp 0.2 It is 115-130 MPa.

3. A method for manufacturing a low-zinc-content 6-series aluminum alloy sheet as described in claim 1 or 2, characterized in that, The manufacturing method includes smelting, casting, homogenization, hot rolling, cold rolling, annealing and solution treatment, pre-aging, and intermediate state feedback. The pre-aging process includes three sections: the first section has a temperature of 95-110℃ and a time of 2-5 min, cooling down to 70-85℃ at a first cooling rate of 1-3℃ / s; the second section has a temperature of 70-85℃ and a time of 2-5 min, cooling down to 45-60℃ at a second cooling rate of 0.5-2℃ / s; and the third section has a temperature of 45-60℃ and a time of 3-6 min. The total pre-aging time is 7-16 minutes.

4. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The homogenization conditions include: a homogenization temperature of 530-560℃ and a homogenization time of 6-16h.

5. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The hot rolling conditions include: a final rolling temperature of 510-530℃, a coiling temperature of 340-380℃, a holding time of 1-2 hours, and self-annealing to 220-260℃ through coiling preheating.

6. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The conditions for cold rolling include: a cold rolling reduction rate of ≥50% and a sheet thickness of 0.8-2.0 mm.

7. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The annealing and solution treatment conditions include: heating at 540-550℃, holding at that temperature for 20-60s, and then spraying or quenching at a third cooling rate of ≥80℃ / min to 30-60℃.

8. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 7, characterized in that, The intermediate state feedback conditions include: 1-2 hours after pre-aging, the conductivity of the plate is tested to be 28-31 MS / m. If the conductivity is >31 MS / m, the heating temperature in the annealing and solution treatment is increased by 5-15℃. If the conductivity is <28 MS / m, the heating temperature in the annealing and solution treatment is decreased by 5-15℃. Alternatively, after the pre-aging is completed, the conductivity of the plate is tested 1-2 hours later and it meets the requirement of 28-31 MS / m. If the conductivity is >31 MS / m, the plate running speed of the solution furnace is reduced by 5-20%. If the conductivity is <28 MS / m, the plate running speed of the solution furnace is increased by 5-20%.

9. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The time from pre-aging to stamping is ≤96h. If the time from pre-aging to stamping is >96h, a stabilization treatment is performed before stamping, specifically, placing it at 90-100℃ for 5-8min.

10. The method for manufacturing low-zinc-content 6-series aluminum alloy sheet according to claim 3, characterized in that, The smelting conditions include: a smelting temperature of 730-760℃ and a smelting time of 2-4 hours; The casting conditions include a casting rate of 3-6 m / h.

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